Convenient superclass for JNDI-based Service Locators. Subclasses are
JavaBeans, exposing a jndiName property. This may or may not include
the "java:comp/env/" prefix expected by J2EE applications. If it doesn't,
it will be prepended.

Subclasses must implement the located() method to cache the results
of the JNDI lookup. They don't need to worry about error handling.

afterPropertiesSet

Invoked by a BeanFactory after it has set all bean properties
supplied.
This method allows the bean instance to perform initialization only possible
when all bean properties have been set and to throw an exception
in the event of misconfiguration.